Rubber and wire mesh ring

ABSTRACT

A back-up ring is disclosed wherein the ring is a knitted mesh section substantially surrounded by an outer coating covering substantially all of the knitted wire mesh section, the coating having contact with the outer and inner surface of an annulus.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 011,338 filed Jan. 29, 1993 for Pack Off Seal, which is acontinuation-in-part of U.S. application Ser. No. 950,820, filed Sep.24, 1992 entitled M-PAC Seal which is a continuation of U.S. applicationSer. No. 512,734, filed May 21, 1990 entitled M-Pac Seal, which is acontinuation of U.S. application Ser. No. 833,690, dated Feb. 25, 1986,now abandoned.

FIELD OF THE INVENTION

[0002] The present invention relates to anti-extrusion rings and, moreparticularly, to wire encapsulated extrusion rings.

BACKGROUND OF THE INVENTION

[0003] Seals have been used to isolate fluids at various pressures andtemperatures. Such seals have existed for use in packing rings, sealrings, piston rings and gland structures in industrial equipment, suchas cylinders, pumps, hydraulics and valves, and in oil field equipment,such as down hole tools and surface equipment, requiring seals, forexample, against high pressure and low pressure liquids and gases.Typically, these seals are annular seals.

[0004] However, under pressure, such seals may be eroded or destroyedand require back-up rings to prevent extrusion of the seal rings. See,for example, U.S. Pat. No. 4,234,197, issued Nov. 18, 1982, Amancharla,et al, entitled Conduit Sealing System. Such systems, however, are bulkyand require additional length. At times they require structures withdifferent materials as back-up rings and require a modules of materialsat escalating values, which must be maintained even at hightemperatures, which is not possible.

[0005] Another illustration of seals, as opposed to back-up rings, usedin the prior art is shown in U.S. Pat. No. 4,524,982 to Hertz, issuedJun. 25, 1985 and entitled Seal for Aggressive Environmnents. Hertzmerely discloses elastomer-impregnated windings of asbestos yamimpregnated into an elastomer to illustrate a seal ring as opposed to aback-up ring, a sort of “steel belted radial” of seals. For similarencapsulated rings, see also, U.S. Pat. No. 4,423,544 to Kashmerick,issued Jan. 3, 1984 for A Method of Making Composite Gasket. For back-uprings, see also, U.S. Pat. No. 3,810,639, issued May 14, 1974, toScanell, entitled Frangible Back-up Ring for Sealing Rings.

[0006] It is an object of the current invention to avoid the distortionsand other problems of the prior art through the use of a non-homogeneouswire encapsulated anti-extrusion ring.

SUMMARY OF THE INVENTION

[0007] A wire encapsulated back-up ring is disclosed having aco-efficient of thermal expansion while the ring is under pressure whichis less than or equal to the surrounding gland metal. The upper surfaceof the back-up ring is concave to allow pressure to energize the back-upring. The outer and inner surfaces normally remain in contact withadjacent portions of the gland and maintain an anti-extrusion barrierfor a scaling ring. The anti-extrusion element also has a lower surfaceadapted to mate with or be a support member behind the anti-extrusionelement. If the back-up ring is not also the support member, the supportmember surface may have a shape as required to hold the element orelements in place. The body of the element includes two parts. The firstpart is a wire mesh, used for reinforcement. Such a part would typicallybe formed in a vee shape, but may deviate to conform to the supportmember. The second part is a coating of sealing material which wouldencapsulate the wire mesh shape. The coating may vary in thicknessaround the wire mesh shape. The coating thickness would depend upon thestrength requirement of the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a further understanding of the nature and objects of thepresent invention, reference is made to the following drawings whichlike parts are given like reference numerals and wherein:

[0009]FIG. 1 is a fragmented side cross-sectional view of the V-Ring ofthe preferred embodiment of the present invention;

[0010]FIG. 2 is a profile view of the V-Ring of one embodiment of thepresent invention;

[0011]FIG. 3 is a fragmentary cross-section view of the seal ring ofFIG. 4;

[0012]FIG. 4 is a second embodiment of the present invention; FIG. 5 isthe knit pattern of the wire mesh used in the metal mesh portion of anypreferred embodiment in the present invention;

[0013]FIG. 6 is an illustration of the mechanism for rolling the wiremesh from a tube of wire mesh to form the wire mesh portion of theback-up rings;

[0014]FIG. 7 is an illustration of the back-up element in place in agland; and

[0015]FIG. 8 is an illustration of the made up seal under pressure.

DESCRIPTION OF THE INVENTION

[0016] As seen in FIG. 1, the back-up ring 5 of the present invention isshown having wire mesh vee shape 50 with an outer coating 100 of sealingmaterial 70. This permits back-up ring 5 with the wire mesh 50 to haveincreased physical strength. The back-up ring 5 retains nearly allphysical strength at high temperatures and thermally expands negligiblycompared to the typical vee ring. The materials are such that aco-efficient of thermal expansion while the back-up ring 5 is underpressure is less than or equal to the surrounding gland metal.

[0017] Referring to FIG. 2, the surfaces of back-up ring 5 include anupper surface 10, which has a modified vee shape with a horizontalportion 11 and angled sides 12, a vertical inner surface 20 and avertical outer surface 30. Surfaces 20, 30 are preferably symmetrical.Surface 10 is concave to allow pressure to energize surfaces 20, 30 ofback-up ring 5. Surfaces 20, 30 remain in contact with their adjacentconduits 120, 130, respectively, and maintain a barrier to flow of thematerial of a seal ring 75 (FIG. 7) at those contact areas. The lowersurface 40 of back-up ring 5 is of a modified vee shape and adapted tomate with a support member 60 behind the seal 5. The upper surface 80 ofthe support member 60 may have any shape required to hold the back-upring 5 in place.

[0018] Thus, the body of the back-up ring 5 has the shape. set out aboveand comprises two parts. The inner part of the body of back-up ring 5includes wire mesh reinforcement 50. Wire mesh reinforcement 50 istypically formed into a vee shape but may deviate slightly to conform tothe upper surface 80 of support member 60.

[0019] The back-up ring 5 as depicted in FIG. 7 is shown annularlybacking up a seal 75 between two conduits 120, 130 by two surfaces 20,30, respectively. Both surfaces have a coating 100 of sealing material70. Such material 70 may be elastomeric, plastic, bonded fibers, orflexible metals, including materials discussed above. The durometerhardness of the material of the coating 100 is preferably between 70 and90 but should not be considered limited to such 70-90 durometer. As tothe preferred material of the coating 100, it is recommended that arubber or rubber type polymer be used for the material 70 which has a 50to 95 durometer reading on the Shore A durometer scale. The durometer ofthe material chosen will be such that the desired sealing effect can besatisfactorily obtained. Any material 70 used in a typical vee ring isacceptable. However, other materials 70 which are not resilient may beused, such as metals, some polymers, or flexible inorganic compounds.The coating 100 of material 70 provide shape maintenance and anon-permeable barrier to well fluids to avoid well fluids from seepinginto the mesh which might cause explosive decompression.

[0020] Surfaces 20, 30, preferably straight sided, remain in contactwith the surfaces oftheir adjacent conduits 120, 130, respectively,during the operation of the back-up ring 5. Because of the shape ofsurface 10 and the angles of all said surfaces 10, 20, 30 relative toeach other, pressure tends to increase contact forces between surfaces20, 30 with conduits 120, 130, respectively. The vee shaped uppersurface 10 is preferably undercut as shown in FIG. 7, such that theback-up ring 5. is pressure sensitive. Further, surface 10 is thinnerthan for a back-up ring for a seal and does not project as far above themesh portion as a seal ring. Further, the surfaces 20, 30 are preferablystraight and do not form an interference with conduits 120, 130 as witha seal ring. Pressure 85 acting on surface 10 through seal 75, as shownin FIG. 8, is converted into load which is communicated through the bodyof back-up ring 5 to surfaces 20, 30, forcing them in back-up againstconduits 120, 130.

[0021] The knitted wire mesh reinforcement 50 may be of any metallic ornon-metallic material that can be drawn into a 0.014 inch diameter wire,or less, and knitted as in FIG. 5. Such knitted wire mesh is that whichis well known in the art, such as shown by Metex Catalogs. Metallicmaterials that can be used include stainless steel, aluminum, copper,brass and the like. Selection of the material is primarily dependent onthe application whether static or dynamic. Other non-metallic materialsthat can be used include organic fibers, inorganic fibers, polymericfilaments, or metallic yarns when knitted as shown in FIG. 5.

[0022] For use, a particularly preferred type of knitted materialcomprises a continuous series of interlocking loops knitted in the formof a tube or stocking 200. The tube 200 is rolled on itself into a donutshape 210 as seen in FIG. 6. The shape is approximate to the finalback-up ring 5 shape. The donut shape is then compressed by compressionmolding and pre-formed into the vee shape of back-up ring 5 of FIG. 1.Density of the wire mesh reinforcement 50 will vary according toapplication but usually is recommended to be between 40-70% of thematerial of the mesh ring, determined by volume and weight. Thiscompressed shape is then coated with a flexible seal material 70. Suchcoating 100 can be applied by vulcanizing or can be by a binder such asan elastomeric material, or a phenolic material or some other suchsynthetic or natural material, either thermo setting or thermoplastic innature, including a fabric reinforced thermo setting or thermoplasticmaterial, or a mixture of thermoplastic/thermo setting material or athermoplastic elastomer, or various combinations of the above, which canbe coated on the knitted material for the wire mesh reinforcement 50,adding chemical adhesion to the mechanical bonding. As a further exampleof the breadth of materials possible, the term “thermal setting”, asused herein, applies to those resins, generally synthetic in nature,which solidify or set on heating and cannot be remelted. Non-limitingexamples of such thermal setting resins include phenolics, amino resins,polyesters, epoxies, silicones and the like. As another example of thebreadth of materials possible, the term “thermoplastic”, as used herein,applies to resins, generally synthetic in nature, that may soften byheat and then regain their control properties upon cooling. Non-limitingexamples of such thermoplastic materials include nylon, polyethylene,polypropylene, cellulose and acrylic resins, polyurethane, syntheticrubbers, teflon, nylon, ryton, polycarbonates and the like. The term“fabric or fibrous material”, as used herein, refers to any materialobtained byweaving or other such techniques wherein the matrix comprisesa latticework of web or thread-like elements. Numerous materials fallinto this class such as, for example, cotton, asbestos, fiberglass,nylon, polyesters, linen, rayon and the like. Furthermore, blends ofvarious materials such as cotton-polyester fabrics, rayon-polyesterfabrics and the like may be employed.

[0023] The outer part of the body of back-up ring 5 includes a coating100 of sealing material 70 which wholly or partially encapsulates thewire mesh reinforcement 50. Typically and preferably, the coating 100will completely surround the wire mesh reinforcement 50. However, thecoating 100 does not need to extend over the entire wire meshreinforcement shape. Also, the coating 100 may vary in thickness aroundthe shape of the wire mesh reinforcement 50. Thickness of coating 100may be specified based on strength requirements of the seal 5.

[0024] Strength of the back-up ring 5 is determined by the physicalproperties of the entire body and is measured by the ability of the ringto remain a back-up ring at a given pressure. Typically the physicalproperties of tensile strength, extrusion resistance, and compressivemodulus of the body materials are in direct relation to the strength ofa back-up ring 5. Relative to a typical vee ring, the wire meshreinforcement member 50 increases the value of all said physicalproperties of the entire seal body.

[0025]FIG. 3 shows a varying geometry that the back-up ring 5 mayembody. Its cross section shown a flat bottom 140 so that besides beinga back-up ring, it also acts as a support member.

[0026] While in the description given above and as depicted in thedrawings, the rings have been described with particular reference toannular members, such as a packing, it is to be understood that theinvention is not so limited. Thus it is not necessary that thegenerallynon-metallic coating 100 or the knit wire mesh reinforcement 50be annular in configuration. Depending on the type of usage to which thering is put, the shape can have virtually any configuration. Forexample, the shape may be elliptical, square, hexagonal or virtually anyother shape. Whatever its shape, the back-up ring 5 would be providedwith the two portions for its body. In general, and except in the caseof an elongate strip type packing material, the back-up ring 5 willgenerally have an opening or passageway therethrough which usually is atleast partially defined by at least a portion of the body of the back-upring 5, sealing being effected in the region generally contiguous insurrounding the opening. Thus, a ring device having a non-annularconfiguration could be used as a back-up between the plug or cock andthe body of a plug valve to ensure that when the valve was either in theopen or the closed position, there was no seal material leakage from theflow passage into the body or the valve in which the plug is mounted. Instatic applications, the back-up ring device would have a highlyasymmetrical configuration as for example in a gasket which has a first,relatively large, generally solid body section attached to a second,lesser volume body section which defined an opening, the opening in thegasket registering with the similar openings in removably fixed parts soas to ensure back-up between the parts at this juncture.

[0027] Because many varying and different embodiments may be made withinthe scope of the inventive concept herein taught including equivalentstructures or materials hereinafter thought of, and because manymodifications may be made in the embodiments herein detailed inaccordance with the descriptive requirements of the law, it is to beunderstood that the details herein are to be interpreted as illustrativeand not in a limiting sense.

What is claimed as invention is: 1) A back-up ring for backing up a sealwith a lower surface for sealing an inner surface and an outer surfaceof an annulus member comprised of a knitted wire mesh; an outer coatingcovering substantially all of said wire mesh member, said outer coatingincluding a first surface with the outer surface of the annulus and asecond surface adjacent the inner surface of the annulus; said memberhaving an upper surface conforming to the shape of the seal. 2) The sealof claim 1, wherein said coating includes: an upper surface having amodified vee shape with angled sides; an outer, vertical surfacedepending from said upper surface; an inner, vertical surface dependingfrom said upper surface; a lower surface joining said outer surface andsaid inner surface. 3) The seal of claim 2, wherein said coating is of amaterial selected from a group consisting of elastomerics, plastics,flexible inorganic compounds, bonded fibers and flexible metals. 4) Theseal of claim 3, wherein said material has a durometer hardness between50 and
 95. 5) The seal of claim 3, wherein said material has a durometerhardness between 70 and
 90. 6) The seal of claim 2, wherein said veeshape is undercut. 7) The seal of claim 1, wherein said knitted wiremesh is of material that can be drawn. 8) The seal of claim 7, whereinsaid knitted wire mesh includes wires having a diameter less than orequal to 0.014 inches. 9) The seal of claim 7, wherein said material isa metal. 10) The seal of claim 7, wherein said material is a non metal.11) The seal of claim 7, wherein said material is a combination of metaland non metal. 12) The seal of claim 7, wherein the density of saidknitted wire mesh is between forty percent and seventy percent of saidmaterial.